Garage doors are commonly manufactured with a number of substantially identical panels which are hinged or pivotally connected together. This allows for pivotal relative movement between adjacent door panels when the garage door is moved between a closed generally vertical position and an open generally horizontal position. Such door panels for many years were predominantly constructed of wood. However, wood door panels are both costly to manufacture and heavy in use, resulting in difficulty when opening and closing the garage door.
Recently, sectional garage door panels having an outer metal skin have become popular and have replaced wooden door panels in many applications. Sectional garage door panels which are rolled or formed by thin sheet metal require either internal reinforcing members, typically constructed of wood or metal, or an irregular cross-section, such as a relief or design or channel shape, to provide the panels with the requisite strength and rigidity. Center and end stiles are often provided within the sheet metal door panel for the required reinforcement.
However, the reinforcing stiles tend to defeat one of the prime advantages of the thin sheet metal door panels; namely, the stiles add additional weight. Therefore, a garage door formed from door panels having reinforcing stiles is difficult and heavy to operate. Additionally, metal door panels even with the reinforcing stiles often do not provide sufficient strength and rigidity for specific garage door applications in which the door is significantly wide and exposed to relatively high velocity winds.
Thin sheet metal door panels are commonly formed having a channel cross-section configuration. However, to provide the needed strength and rigidity, the channel section of the sheet metal door panel is significantly thick, thereby increasing the garage door weight. Such channel-shaped door panels are designed for the purpose of increasing the strength of the door, but these channel-shaped panels having relatively thick metal skins are not adapted for many garage door applications requiring both light weight and increased strength.
To add both increased strength and thermal insulation protection, a foam core is often included in the channel door panels previously described. The foam insulation core increases the resistance of the thin metal skin door panel to deflect and warp due to impacting wind or other tensile loads.
The foam insulation core within the sheet metal door panel can provide required strength and rigidity without the increased weight associated with wooden or metal stiles or other reinforcing members. The problem with using the foam insulation core to provide the strength and rigidity in a thin metal skin door panel is that the foam insulation core must be of substantial thickness throughout the cross-section of the door panel. The added thickness of foam insulation requires added production and material costs when fabricating such a door panel.
As evidenced by the above background, there is an existing need for a metal skin garage door panel which provides the required strength and rigidity to withstand the wind and structural loads associated with many garage door applications while remaining lightweight. Furthermore, the garage door panel must be easily and economically manufactured with a minimum of component parts while providing the identified physical attributes.